Re: [prefix=PATCH] drivers: pmbus: core: Prevent calling pmbus_set_page with negative page

Guenter Roeck
2017-10-25T21:12:37Z

On Wed, Oct 25, 2017 at 02:52:53PM -0500, Eddie James wrote:
> From: "Edward A. James" <eajames@us.ibm.com>
>
> For devices with word data registers, the pmbus core may call read/write
> word data functions with a page value of -1, in order to perform the
> operation without setting the page. However, the read/write word data
> functions accept only unsigned 8-bit page numbers, resulting in setting
> a page of 0xFF in this situation. This may result in errors or undefined
> behavior of some devices (specifically the ir35221, which allows the
> page to be set to 0xFF, but some subsequent operations to read registers
> may fail).
>

Good catch.

Subject came off a bit odd.

[prefix=PATCH] drivers: pmbus: core: Prevent ...

Please use "[PATCH] hwmon: (pmbus/core) Prevent ..."

This me wonder if we should move the check into pmbus_set_page()
instead.

int pmbus_set_page(struct i2c_client *client, int page)
{
...
if (page >= 0 && page != data->currpage) {
...
}

What do you think ?

Thanks,
Guenter

> Signed-off-by: Edward A. James <eajames@us.ibm.com>
> ---
> drivers/hwmon/pmbus/pmbus.h | 4 ++--
> drivers/hwmon/pmbus/pmbus_core.c | 29 ++++++++++++++++++-----------
> 2 files changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
> index 4efa2bd..4a16da6 100644
> --- a/drivers/hwmon/pmbus/pmbus.h
> +++ b/drivers/hwmon/pmbus/pmbus.h
> @@ -405,8 +405,8 @@ struct pmbus_driver_info {
>
> void pmbus_clear_cache(struct i2c_client *client);
> int pmbus_set_page(struct i2c_client *client, u8 page);
> -int pmbus_read_word_data(struct i2c_client *client, u8 page, u8 reg);
> -int pmbus_write_word_data(struct i2c_client *client, u8 page, u8 reg, u16 word);
> +int pmbus_read_word_data(struct i2c_client *client, int page, u8 reg);
> +int pmbus_write_word_data(struct i2c_client *client, int page, u8 reg, u16 word);
> int pmbus_read_byte_data(struct i2c_client *client, int page, u8 reg);
> int pmbus_write_byte(struct i2c_client *client, int page, u8 value);
> int pmbus_write_byte_data(struct i2c_client *client, int page, u8 reg,
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index 302f0ae..6d6e030 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -186,13 +186,16 @@ static int _pmbus_write_byte(struct i2c_client *client, int page, u8 value)
> return pmbus_write_byte(client, page, value);
> }
>
> -int pmbus_write_word_data(struct i2c_client *client, u8 page, u8 reg, u16 word)
> +int pmbus_write_word_data(struct i2c_client *client, int page, u8 reg,
> + u16 word)
> {
> int rv;
>
> - rv = pmbus_set_page(client, page);
> - if (rv < 0)
> - return rv;
> + if (page >= 0) {
> + rv = pmbus_set_page(client, page);
> + if (rv < 0)
> + return rv;
> + }
>
> return i2c_smbus_write_word_data(client, reg, word);
> }
> @@ -219,13 +222,15 @@ static int _pmbus_write_word_data(struct i2c_client *client, int page, int reg,
> return pmbus_write_word_data(client, page, reg, word);
> }
>
> -int pmbus_read_word_data(struct i2c_client *client, u8 page, u8 reg)
> +int pmbus_read_word_data(struct i2c_client *client, int page, u8 reg)
> {
> int rv;
>
> - rv = pmbus_set_page(client, page);
> - if (rv < 0)
> - return rv;
> + if (page >= 0) {
> + rv = pmbus_set_page(client, page);
> + if (rv < 0)
> + return rv;
> + }
>
> return i2c_smbus_read_word_data(client, reg);
> }
> @@ -269,9 +274,11 @@ int pmbus_write_byte_data(struct i2c_client *client, int page, u8 reg, u8 value)
> {
> int rv;
>
> - rv = pmbus_set_page(client, page);
> - if (rv < 0)
> - return rv;
> + if (page >= 0) {
> + rv = pmbus_set_page(client, page);
> + if (rv < 0)
> + return rv;
> + }
>
> return i2c_smbus_write_byte_data(client, reg, value);
> }
> --
> 1.8.3.1
>